You didn't say when the top branches were whacked off; you might have done it too early in the season. There are lots of reasons that fruit trees don't bear edible fruit, or a lot of it: a late frost that damaged buds for the season; heavy winds that dried out the buds; inadequate cross-pollination; pruning before the June fruit-drop. Prune after June. Too soon, and you might be "whacking off" fruit buds. Also, if you happened to "top" the tree--hacking off the ends of branches--those branches will never grow back. Trees grow from the roots. You might have effectively kiled the tree. That kind of stress could result in inedible fruit.